This invention relates generally to a xerographic development apparatus incorporating an improved agitation article which apparatus controllably and accurately conveys particulate imaging materials from a sump reservoir to an imaging member. More specifically the invention concerns a single component xerographic development apparatus and an agitation article therein which apparatus improves the flowability and the supply of imaging particulate materials, such as magnetic and non-magnetic toner particles, to a photoreceptor. The apparatus and article improve the overall imaging performance and imaging quality of printing machines that incorporate the improved hardware. The improved development apparatus solves the so-called "white banding" image defect problem.
The article, apparatus, and imaging method of the present invention solves important particulate transport and development problems and provides various advantages including: improved developer agitation; improved developer circulation; improved developer charging and developability; reduced or eliminated white banding image defects; increased development apparatus reliability; reduced downtime for blockage or leakage problems associated with the prior art development apparatus; preventing localized developer and toner agglomeration in the area near the donor roll; providing improved developer circulation between the sump and the surface of the donor roll; and improving developer charging stability.
One-component and two-component developer systems utilize toner that can be difficult to flow and charge controllably. This is particularly true of the toner used in one component systems. The toner tends to cake and bridge within the sump or within the developer housing. Also, this tendency to cake and bridge may cause soft blocked toner cakes to form within the developer housing which cakes can distort the charging of the toner and produce image defects in the printed images.
In addition, the developer on the donor roll often suffers severe high mechanical stress under low toner throughput condition. This is because the developer on the donor roll cannot readily get off the donor roll and circulate well with the developer in the housing. This stressed developer has poor powder flow, poor charging stability, and lower charge. Consequently, the solid area density of the prints decreases and the background grayness increases.
These and other problems are solved with the article, development apparatus, and imaging method of the present invention.